Materials may change their size and shape such as by expanding or contracting when subjected to various forces such as heat, mechanical stress, electricity, and the like. Most materials expand when heated, for example, and the amount and rate of this expansion must be considered when designing devices which will be subjected to temperature changes. The coefficient of linear thermal expansion represents the ratio of change of length to the actual (original) length per degree temperature change. Typically, this ratio is expressed as the fractional change in length of a material per degree of temperature change. Engineering and construction applications where temperature changes are expected must take the expansion and contraction of materials into account.
The coefficient of thermal expansion of a material can be measured with the use of a dilatometer. Dilatometers typically consist of a heat source, such as a furnace, and a means for measuring the expansion of the material being tested. Capacity dilatometers measure the expansion of a material using capacitor having one movable and/or flexible plate. Expansion of the material being tested moves the plate relative to the fixed plate thereby changing the capacitance of the capacitor. The change in capacitance is then used to calculate the change in distance between the capacitor's plates which is equal to the change in the length of the material being measured. Other dilatometers measure the expansion of the sample material using a strain gauge.
Most commercially available dilatometers are large and expensive pieces of equipment. Additionally, many are equipped with heat sources capable of reaching temperatures in excess of 1000° Celsius making them unsuitable for certain applications such as educational science labs. There remains a need for a less expensive but highly accurate means for determining the coefficient of thermal expansion of materials. Additionally, there is also a need for the ability to accurately measure very small changes in the size of materials when they are subjected to a variety of stresses other than temperature changes.